1 . Field of the Invention
The invention is directed to an improved pressure regulator for a fuel supply system of an internal combustion engine for regulating a fuel pressure, including a valve which includes a valve ball that is forced against a valve seat into the closing position by the action of a valve leaf spring.
2 . Description of the Prior Art
One pressure regulator of the type with which this invention is concerned is described by German Patent Disclosure DE 101 07 223A1, in which the valve leaf spring is pivotably supported, and one arm of the valve leaf spring toward the valve seat with respect to the pivotable support is braced on the valve ball, while one arm of the valve leaf spring located on the side opposite the valve seat is braced on a support body, in such a way that torque equilibrium prevails at the valve leaf spring. The prestressing force generated by the support body is transmitted by the valve leaf spring to the valve ball in the form of closing force. If fuel pressure that is high enough to generate a greater pressure force than the closing force acting on the valve ball prevails at the pressure input, then the valve ball lifts from the valve seat and opens a defined flow cross section, so that fuel can flow to the pressure outlet. SUMMARY AND ADVANTAGES OF THE INVENTION
Without the impact face according to the present invention, the force exerted by the valve leaf spring on the valve ball of the known regulator increases steadily as the flow becomes greater and consequently the valve ball stroke lengthens. Since an equilibrium of force or moment ensues at the valve leaf spring, the result is that with an increasing flow, the fuel pressure likewise increases, in a way that is unwanted for a pressure regulator.
As a result of the definitive characteristics of the invention a comparatively lesser increase in the characteristic pressure and flow curve of the pressure regulator is obtained; therefore even if the flow quantity increases, the set pressure becomes only slightly greater. When the valve ball has lifted from the valve seat, the deflection according to the invention of the fuel flow to the impact face creates a flow force that acts on the valve leaf spring counter to the closing force of the valve leaf spring and that is greater, the greater the flow through the valve of the pressure regulator. Thus with a greater flow and a consequent longer stroke of the valve ball, on the one hand the force exerted by the elastic valve leaf spring on the valve ball in the closing direction increases, but on the other hand, the contrary flow force on the valve leaf spring also increases, so that these forces at least partly compensate for one another. As a result, the influence of the stroke of the valve leaf spring and thus the influence of the flow on the pressure are advantageously less.
In a preferred embodiment, the impact face is formed by a portion of a lower face of the valve leaf spring, which portion is adjacent to a contact point of the valve ball with the valve leaf spring. This is especially advantageous in terms of production costs, since because of the integration of the impact face with the valve leaf spring, no additional components are necessary.
In order to deflect the fuel flow, flowing around the valve ball, onto the impact face at the valve leaf spring, the valve seat preferably has a cone angle in a range between 40° and 110°, preferably 60°.
In a further embodiment, the impact face is formed by a face that is defined at the valve ball and extends radially outward into the fuel flow. As a result, the fuel flow flowing around the valve ball can strike the impact face nearly perpendicularly, and this is an ideal state in terms of the flow force generated as a result.
In an especially preferred embodiment, the valve leaf spring is provided with at least one opening, which increases in cross section in a direction pointing away from a leaf spring bearing point. As a result, if the valve leaf spring bends, a substantially constant tension ensues over the length, and the spring constant of the valve leaf spring becomes relatively low; changes in the stroke of the valve ball therefore have a lesser effect on the pressure. In the preferred embodiment, in which the impact face is located on the valve leaf spring, the opening is located outside the impact face, in order not to hinder the buildup of the flow force.
A refinement provides that the valve leaf spring is embodied as rectangular and the opening is embodied as essentially triangular. The valve leaf spring is preferably supported tiltably at a pivot shaft, and one arm of the valve leaf spring is tensed against a prestressing spring for generating a force by which the other arm of the valve leaf spring holds the valve ball down in the valve seat. Then, both arms of the valve leaf spring are provided with at least one triangular opening, since they both contribute to the overall bending strength of the valve leaf spring.